This invention relates generally to data storage drives having a removable storage medium and more specifically relates to security of data on the removable medium such as confirmation of data integrity and determination of whether data has been read or written by unauthorized persons.
For computer readable data, there is a general need for confirmation of data integrity. That is, there is a need to be able to determine whether data has been modified. In addition, sometimes there is a need to see whether data has been read, particularly by someone not authorized to read the data. Data security is a particular concern for removable storage media such as flexible disks, removable hard disk cartridges, tape cartridges, and writeable optical disks. For removable rewritable media that can be easily mailed or otherwise transferred from one system to another, there is a particular need for aids to help detect tampering or unauthorized reading.
A secure media access audit trail is provided by requiring drives to record a drive identification on a writeable medium each time the medium is accessed by the drive. As a result, a possessor of a writable medium can identify the last N distinct drives that have accessed the medium, and the drives that accessed the medium the last M times, where N and M are maximum numbers that are medium dependent. Depending on the need of the possessor of a medium, it may be sufficient to track loading of a medium into a drive. As an alternative, or as an addition, it may be preferable to track reading, if unauthorized reading is the primary concern, or writing, if data integrity is the primary concern. In the present patent document, the word xe2x80x9caccessxe2x80x9d is intended to include loading, reading, writing, or any other trackable drive/medium events of interest. All compatible storage drives that are capable of writing to a particular medium are required to participate in the access audit process. Preferably, compatible drives have an electronically readable identifier, that includes, for example, a unique manufacturer code, drive model number, and drive serial number. Alternatively, a drive identification may be generated by a host computer software device driver in combination with a drive. A portion of the medium is dedicated to a Unique Drive Table, which, for example, may be a circular buffer, that stores the drive identifiers of the last N distinct drives to access the medium. In addition, a portion of the medium is dedicated to a Access Audit Table, that can store a fixed number (M) of drive identifiers. Any time a writable medium is accessed, the drive must automatically write the drive identifier to the Access Audit Table. Compatible systems must reject any external commands to write to the Unique Drive Table or to the Access Audit Table.
The method of the invention is useful, for example, to enable a computer operator to determine for a particular medium, a list of the different drives in which the medium has been accessed, and the sequential order of drives into which the medium has been accessed. This information in turn may be useful to determine whether the data on the medium may have been modified or read by unauthorized persons.